Continuous hydroformulation process for producing an aldehyde

ABSTRACT

A continuous hydroformylation process for producing an aldehyde comprising 1) reacting an olefinically unsaturated compound, carbon monoxide and hydrogen in the presence of a rhodium-organobisphosphite complex catalyst at a partial pressure of carbon monoxide and hydrogen, and 2) exposing a mixture comprising at least a portion of the catalyst of 1) to a gaseous mixture comprising hydrogen at a pressure that is greater than the partial pressure of carbon monoxide and hydrogen during the reaction.

The invention relates to a continuous hydroformylation process forproducing an aldehyde comprising 1) reacting an olefinically unsaturatedcompound, carbon monoxide and hydrogen in the presence of arhodium-organobisphosphite complex catalyst at a partial pressure ofcarbon monoxide and hydrogen.

It is well known in the art that aldehydes may be readily produced byreacting an olefinically unsaturated compound with carbon monoxide andhydrogen in the presence of a rhodium-organophosphorous ligand complexcatalyst and that preferred process involved continuous hydroformylationand recycling of the catalyst solution such as disclosed, for example,in U.S. Pat. Nos. 4,148,830; 4,717,775; and 4,769,498. Organophosphites,especially organobisphosphites, have proven to be among the ligands ofchoice in rhodium catalyzed hydroformylation reactions because suchcomplexes exhibit exceptional activity and regioselectivity in thisreaction. For instance, U.S. Pat. Nos. 4,668,651 and 4,769,498 fullydetail such hydroformylation.

However, although rhodium catalyzed hydroformylation reactions haveenjoyed a wealth of commercial development, efficiency and costassociated with these processes remain a primary concern, especially inlight of the scarcity and high price of rhodium metal, as well as thecosts associated with organobisphosphite ligands. Traditional attemptsto improve the reaction rate, as well as reduce costly decompositionpathways of the metal complex catalysts and/or ligand have focused onligand choice, as described above, or reaction conditions. For example,U.S. Pat. Nos. 5,288,918 and 5,763,670 describe catalyst protection andincreased longevity through the addition of additives, or manipulationof the reaction conditions.

Yet the rate of the hydroformylation reaction is often reduced by thepresence of other compounds in the reaction mixture which may form morestable, yet less reactive rhodium species. Such compounds producerhodium complexes which do not catalyze the desired hydroformylationreaction and therefore slow down the rate of hydroformylation, requiregreater amounts of rhodium, and turn, increase the cost of thehydroformylation process.

One such class of compounds are organic species which contain multiplealkene functionalities, usually alkadienes. These compounds act as atype of poison towards the metal center by complexing or reacting withit. The resulting rhodium alkadiene complex is thus prevented fromentering the desired reaction pathway of hydroformylation, because sucha pathway would require the energetically favored coordinated alkadieneto be first displaced in order to react with the desired olefinicallyunsaturated compound, carbon monoxide, and hydrogen.

Since many of the olefinically unsaturated compounds which arecommercially hydroformylated are synthesized from, or contain asimpurities, alkadienes, these catalyst poisons are often present intypical hydroformylation processes. As a result, much rhodium metal isprevented from participating in the hydroformylation process, whichcorresponds to increased production costs for aldehydes produced bythese processes. Accordingly, a method by which these poisons could beprevented from interfering with the catalyst would be a greatimprovement in the hydroformylation process.

The object of the invention is to prevent or at least minimize decreasein reaction rate in rhodium-organobisphosphite complex catalyzedcontinuous hydroformylation processes.

This object is achieved in that the process also comprises 2) exposing amixture comprising at least a portion of the catalyst of 1) to a gaseousmixture comprising hydrogen at a pressure that is greater than thepartial pressure of carbon monoxide and hydrogen during the reaction.

The pressure at which the mixture comprising at least a portion of thecatalyst of 1) is treated, i.e. the pressure used in step 2) is alsoreferred to as activating pressure. By activating pressure, it is meanta pressure which is greater than the partial sum of the pressures ofcarbon monoxide and hydrogen during the hydroformylation reaction.

The gaseous mixture comprises hydrogen or preferably comprises hydrogenand carbon monoxide.

It has been found that alkadiene and especially conjugated alkadienepoisoning of the catalyst is minimized or reversed by carrying out apart of said process at an activating pressure of hydrogen or atactivating pressures of hydrogen and carbon monoxide.

Accordingly, the subject invention encompasses reversing or minimizingthe catalyst deactivation associated with alkadiene poisoning ofrhodium-organobisphosphite complex catalyzed hydroformylation processesfor producing aldehydes, by treating a mixture comprising at least aportion of the catalyst used in the hydrofomylation reaction at anactivating pressure of hydrogen or of carbon monoxide and hydrogen.Preferably, the activating pressure is a pressure between 3 MPa and 20MPa of a mixture of gases comprising hydrogen or comprising hydrogen andcarbon monoxide. Still more preferably the activating pressure isbetween between 3 and 10 MPa. If it is chosen to reverse or minimize thecatalyst deactivation associated with alkadiene poisoning ofrhodium-organobisphosphite complex catalyzed hydroformylation processesfor producing aldehydes, by performing part of this process at anactivating pressure of carbon monoxide and hydrogen, the pressure ispreferably equal to the combined hydrogen and carbon monoxide pressure.The molar ratio of hydrogen and carbon monoxide is between 10:1 and1:10, preferably between 6:1 and 1:1 and more preferably between 2:1 and1:1. The temperature at which the the catalyst deactivation associatedwith alkadiene poisoning of rhodium-organobisphosphite complex catalystsis reversed, prevented or at least minimized is preferably between 25°C. and 200° C., more preferably from 70° C. to 120° C. and mostpreferably from 90° C. to 100° C.

The mixture which in the process of the invention is exposed to agaseous mixture comprising hydrogen at an activating pressure greaterthan the partial pressure of hydrogen and carbon monoxide during thehydroformylation reaction is preferably at least a portion of thehydroformylation reaction mixture or at least a portion of the reactionmixture obtained between the hydroformylation reaction zone and theseparation zone in which separation zone the desired aldehyde product isseparated off.

A preferred embodiment of the present invention is a continuoushydroformylation process for producing an aldehyde comprising reacting arhodium-organobisphosphite complex catalyst, carbon monoxide, hydrogen,and an olefinically unsaturated compound, to form a hydroformylationreaction mixture wherein said hydroformylation reaction mixture isdistilled into an aldehyde product containing stream and a recyclablecatalyst containing stream, and wherein said carbon monoxide andhydrogen are both maintained at independent minimum partial pressuresduring the reaction, and wherein a least a portion of saidhydroformylation reaction mixture is exposed to an activating pressureof a gaseous mixture comprising hydrogen or comprising hydrogen andcarbon monoxide prior to distillation which activating pressure isgreater than said minimum pressures. Generally, the reaction mixtureremoved from the hydroformylation reaction zone (the hydroformylationreaction mixture) is subjected to a pressure reduction so as tovolatilize and remove a substantial portion of the unreacted gasesdissolved in the reaction mixture and then pass the so-obtained liquidreaction mixture which now contains a much lower syn gas concentrationthan was present in the reaction mixture leaving the hydroformylationreaction zone (the so-called hydroformylation reaction mixture) to thedistillation zone e.g. vaporizer/separator, wherein the desired aldehydeproduct is distilled. In a preferred embodiment of the invention, atleast a part of the hydroformylation reaction mixture or the liquidreaction mixture obtained by removing a substantial portion of unreactedcarbon monoxide and hydrogen gases is exposed to a gasesous mixturecomprising hydrogen or comprising hydrogen and carbon monoxide at anactivating pressure greater than the partial pressure during thehydroformylation reaction. Without wishing to be bound to any theory itis believed to be advantageous to expose at least a part of thehydroformylation reaction mixture or at least a part of the reactionmixture obtained by removing from the hydroformylation reaction mixturea substantial portion of unreacted carbon monoxide and hydrogen to thegaseous mixture prior to distillation of such reaction mixture becausethe released alkadiene or hydroformylation product thereof can beseparated in the distillation zone wherein the desired aldehyde isdistilled and can be removed from the hydroformylation process togetherwith the desired aldehyde product.

In an even more preferred embodiment of the invention, at least a partof the hydroformylation reaction mixture is exposed to a gaseous mixturecomprising hydrogen or comprising carbon monoxide and hydrogen at anactivating pressure which is greater than the partial pressure duringthe reaction.

In yet another preferred embodiment of the present invention theactivating pressure of either hydrogen or hydrogen and carbon monoxideis between 3 and 20 MPa. More preferably it is between 3 and 10 MPa.

In another embodiment of the present invention, the activating pressureis maintained over a part of the reaction mixture in a vessel differentfrom that containing the reaction mixture. Other objects and advantagesof this invention will become readily apparent from the followingwritten description and appended claims.

A rhodium bisphospite complex catalyzed hydroformylation reactiontypically involves the exposure of an olefinically unsaturated compoundto molecular hydrogen and carbon monoxide in the presence of a rhodiumbisphospite complex catalyst, to obtain one or more product aldehydes.The olefinically unsaturated compounds employed in the hydroformylationprocess often contain impurities. Typical impurities include water,oxygen, and other olefinically unsaturated compounds. Among the mostharmful impurities present within the olefinically unsaturated reactantare multi-unsaturated conjugated organic compounds. Included in thisclass of contaminants are compounds containing at least two alkenefunctionalities, such as alkadienes and alkatrienes. Especially theconjugated alkadienes and alkatrienes are harmful under normalhydroformylation conditions. Examples thereof are 1,3-butadiene, 1-vinylcyclohexene, 1,3,7-octatriene. Such impurities are believed to react orcomplex with the rhodium organobisphosphite catalysts, or itsprecursors, in a competitive fashion. The rhodium-olefin complexes whichresult from these competitive impurity reactions are less reactive incatalyzing the desired hydroformylation reaction. As a result, thepresence of these impurities often slows or halts the hydroformylationprocess. Thus the inventors of the present invention sought a means bywhich a rhodium complex catalyst may maintain its activity towardscatalysis of the desired hydroformylation reaction.

As stated above, the subject invention resides in the discovery thatalkadiene deactivation of such rhodium-organobisphosphite complexcatalysts during the hydroformylation process, can be minimized orprevented by treating at least a portion of the reaction mixture with anactivating pressure of hydrogen or of a mixture comprising carbonmonoxide and hydrogen. The increase in the activating pressure may beperformed intermittently or continuously, but is more preferablyconducted in one or more discrete periods during the hydroformylation.If it is chosen to increase the partial pressure of carbon monoxidesimultaneously with the partial pressure of hydrogen in order to achievethe activating pressure, then it is preferable to maintain this increasein carbon monoxide pressure for the same duration as the activatingpressure of hydrogen is maintained.

In the present invention, the activating pressure may be maintainedwithin the reaction vessel or within a separate vessel. If a separatevessel is employed, portions of the reaction mixture to be activated maybe withdrawn and transferred to said separate vessel at any time duringthe hydroformylation process by any conventional manipulation, and thenreturned to the hydroformylation process following activation andpreferably returned to the reaction zone of the hydroformylationprocess. Alternately, a continuous stream of reaction mixture may bewithdrawn from the hydroformylation process and exposed to theactivating pressure within a separate vessel, before being returned tothe remainder of the reaction mixture. The term “reaction mixture” asused herein is understood to include the following substances presentwithin the hydroformylation process: rhodium-organobisphosphite complexcatalyst, solvent, and optionally unconverted olefinically unsaturatedcompound, any product aldehyde, carbon monoxide and hydrogen. The term“hydroformylation reaction mixture” as used herein is understood toinclude the following substances present within the hydroformylationprocess: rhodium-organobisphosphite complex catalyst, solvent, anyunconverted olefinically unsaturated compound, any product aldehyde,and, optionally, carbon monoxide and hydrogen. With the term“hydroformylation reaction mixture” is meant the mixture which isobtained by reacting an olefinically unsaturated compound, carbonmonoxide and hydrogen in the presence of a rhodium organobisphosphitecomplex catalyst.

Without wishing to be bound to any exact theory or mechanisticdiscourse, decreased catalytic activity of therhodium-organobisphosphite complex in the presence of alkadienes mostlikely occurs as the result of the formation of coordinatively saturatedrhodium-alkadiene complexes (second state catalyst complex). Thesecomplexes lack a means to coordinate another ligand, such as theolefinically unsaturated substrate, under typical hydroformylationconditions. However, under an activating pressure of carbon monoxide andhydrogen gas, these complexes may enter into a process by which thecatalyst poisoning alkadiene ligand may itself be hydroformylated. As aresult of this invention, the poisoning alkadiene is converted into forinstance an aldehyde, thereby releasing active rhodium. The rhodiummetal is than free to reenter the catalytic cycle as a reactive rhodiumhydride or hydrido-carbonyl complex (first state catalyst complex). Thesecond state catalyst complex is less effective in catalyzing thehydroformylation reaction than is the first state catalyst complex.Treating a mixture comprising at least a portion of the second statecatalyst complex at a partial pressure of hydrogen or at a partialpressure of carbon monoxide and hydrogen which is greater than the sumof the partial pressures of hydrogen and carbon monoxide during thereaction allows for the catalyst complex to become in the first state.

The recuperation of the catalytic activity of therhodium-organobisphosphite complex catalyst obtained according to thisinvention may be determined and confirmed by any suitable conventionalprocedure for ascertaining an increase in the productivity of theprocess. Preferably the process of this invention may be easilyevaluated by carrying out comparative hydroformylation reactions andcontinuously monitoring their rates of hydroformylation. The differencein hydroformylation rate (or difference in catalyst activity) may thenbe observed in any convenient laboratory time frame. For instance,reaction rate may be expressed in terms of gram-moles of aldehydeproduct produced per liter of catalyst solution per hour of reaction,which rate, if desired, may be adjusted for varying olefin partialpressures by dividing said rate by the olefin partial pressure.

In a preferred embodiment of the present invention therhodium-bisphosphite complex catalyst comprises a bisphosphite ligand ofa formula selected from the group consisting of:

wherein each R¹ represents a divalent radical selected from a groupconsisting of alkylene, alkylene-(Q)_(n)-alkylene, arylene andarylene-(Q)_(n)-arylene, and wherein each alkylene radical individuallycontains from 2 to 18 carbon atoms and is the same or different, andwherein each arylene radical individually contains from 6 to 18 carbonatoms and is the same or different; wherein each Q individuallyrepresents a divalent bridging group of —O— or —CR′R″— wherein each R′and R″ radical individually represents hydrogen or a methyl radical; andwherein each n individually has a value of 0 or 1,wherein R², R³, R⁴, and R⁵ might be the same or different and each isindividually represented by the structure of (VI) or (VII),

wherein R⁶ and R⁷ might be the same or different and each isindividually represented by the structure of (VIII) or (IX),

wherein X⁵ and X⁶ might be the same or different and each individuallyrepresents a hydrogen or an organic radical, wherein Y³, Y⁴ and Y⁵ arethe same or different and each represents a hydrogen or alkyl radical,wherein Z⁵, Z⁶, Z⁷, Z⁸, Z⁹, Z¹⁰ and Z¹¹ might be the same or differentand each represent a hydrogen or an organic radical placed at anyremaining position of the aryl rings.

In a more preferred embodiment of the present invention, R¹ isrepresented by the structure of (IV), (V),

(VIII), (IX), wherein (Q)_(n) is the same as above, wherein X¹, X², X³,X⁴, X⁵ and X⁶ might be the same or different and each individuallyrepresents a hydrogen or an organic radical, wherein Y¹, Y², Y⁴ and Y⁵are the same or different and each represents a hydrogen or alkylradical, wherein Z¹, Z², Z³, Z⁴, Z⁸, Z⁹, Z¹⁰ and Z¹¹ might be the sameor different and each represent a hydrogen or an organic radical placedat any remaining position of the aryl rings.

In an even more preferred embodiment of the present invention R¹ isrepresented by the structure of (IV), (V), (VIII), (IX), wherein (Q)_(n)is the same as above, wherein X¹ is the same as X² and Z¹ is the same asZ² in Formula (IV), X³ is the same as X⁴, Z³ is the same as Z⁴, and Y¹and Y² are hydrogen radicals in Formula (V), Z⁸ is the same as Z⁹ inFormula (VIII), Z¹⁰ is the same as Z¹¹ and Y⁴ and Y⁵ are hydrogenradicals in Formula (IX).

Still more preferably said hydroformylation process is performed whereinsaid ligand used is chosen from the group consisting of[3,3′-bis(t-butyl)-5,5′-dimethoxy-1,1′-biphenyl-2,2′-diyl]-bis(oxy)]-bis(dibenzo[d,f][1,3,2])dioxaphosphepin,3,3′-bis(carboxyisopropyl)-1,1′-binaphthyl-2,2-diyl-bis[bis(1-naphthyl)]phosphiteand3,3′-bis(carboxymethyl)-1,1′-binaphthyl-2,2′-diyl-bis[bis(2,5-di-t-butyl)]phosphite.

Illustrative rhodium-bisphosphite complex catalysts employable in suchhydroformylation reactions encompassed by this invention may includethose disclosed in the above mentioned patents wherein the bisphosphiteligand is a ligand selected from the class consisting of Formulas (I),(II) and (III) above. In general, such catalysts may be preformed, orformed in situ, as described e.g., in said U.S. Pat. Nos. 4,668,651 and4,769,498, and consist essentially of rhodium in complex combinationwith the organobisphosphite ligand. It is believed that carbon monoxideis also present and complexed with the rhodium in the active species.The active catalyst species may also contain hydrogen directly bonded tothe rhodium.

As noted above illustrative organobisphosphite ligands that may beemployed as the bisphosphite ligand complexed to the rhodium catalystand/or any free bisphosphite ligand (i.e. ligand that is not complexedwith the rhodium metal in the active complex catalyst) in suchhydroformylation reactions encompassed by this invention include thoseof Formulas (I), (II), and (III) above.

Illustrative divalent radicals represented by R¹ in the abovebisphosphite formulas (I), (II) and (III) include substituted andunsubstituted radicals selected from the group consisting of alkylene,alkylene-(Q)_(n)-alkylene, phenylene, naphthylene,phenylene-(Q)_(n)-phenylene and naphthylene-(Q)_(n)-naphthyleneradicals, and where Q, and n are the same as defined above. Morespecific illustrative divalent radicals represented by R¹ are shown bythe structure of (IV) or (V) wherein (Q)_(n) is the same as above. Theseinclude, 1,1′biphenyl-2,2′-diyl, 3,3′-dialkyl-1,1′-biphenyl-2,2′-diyl,3,3′-dicarboxy ester-1,1′-biphenyl-2,2′-diyl, 1,1′binaphthyl-2,2′-diyl,3,3′-dicarboxy ester-1,1′-binaphthyl-2,2′-diyl,3,3′-dialkyl-1,1′-binaphthyl-2,2′-diyl, 2,2′-binaphthyl-1,1′-diyl,phenylene-CH₂-phenylene, phenylene-O-phenylene,phenylene-CH(CH₃)-phenylene radicals, and the like.

Illustrative radicals represented by Z¹, Z², Z³, Z⁴, Z⁵, Z⁶, Z⁷, Z⁸, Z⁹,Z¹⁰, and Z¹¹ in above Formulas (IV) to (IX), in addition to hydrogen,include any of those organic substituents containing from 1 to 18 carbonatoms, disclosed in U.S. Pat. No. 4,668,651, or any other radical thatdoes not unduly adversely effect the process of this invention.Illustrative radicals and substituents encompass alkyl radicals,including primary, secondary and tertiary alkyl radicals such as methyl,ethyl n-propyl, isopropyl, butyl, sec-butyl, t-butyl, neo-pentyl,n-hexyl, amyl, sec-amyl, t-amyl, iso-octyl, decyl, octadecyl, and thelike; aryl radicals such as phenyl, naphthyl and the like; aralkylradicals such as benzyl, phenylethyl, triphenylmethyl, and the like;alkaryl radicals such as tolyl, xylyl, and the like; condensated arylradicals such as phenylene, naphthylene, and the like, alicyclicradicals such as cyclopentyl, cyclohexyl, 1-methylcyclohexyl,cyclooctyl, cyclohexylethyl, and the like; alkoxy radicals such asmethoxy, ethoxy, propoxy, t-butoxy —OCH₂CH₂OCH₃, —O(CH₂CH₂)₂OCH₃,—O(CH₂CH₂)₃OCH₃, and the like; aryloxy radicals such as phenoxy and thelike; as well as silyl radicals such as —Si(CH₃)₃, —Si(OCH₃)₃,—Si(C₃H₇)₃, and the like; amino radicals such as —NH₂, —N(CH₃)₂, —NHCH₃,—NH(C₂H₅), and the like; acyl radicals such as —C(O)CH₃, —C(O)C₂H₅,—C(O)C₆H₅, and the like; carbonyloxy radicals such as —C(O)OCH₃,—C(O)OCH(CH₃)₂—(C(O)CH(CH₃)C₈H₁₇, and the like; oxycarbonyl radicalssuch as —(CO)C₆H₅, and the like; amido radicals such as —CONH₂,—CON(CH₃)₂, —NHC(O)CH₃, and the like; sulfonyl radicals such as—S(O)₂C₂H₅ and the like; sulfinyl radicals such as —S(O)CH₃ and thelike; thionyl radicals such as —SCH₃, —SC₂H₅, —SC₆H₅, and the like;phosphonyl radicals such as —P(O)(C₆H₅)₂, —P(O)(CH₃)₂, —P(O)(C₂H₅)₂,—P(O)(C₃H₇)₂, —P(O)CH₃(C₆H₅), —P(O)(H)(C₆H₅), and the like.

Illustrative radicals represented by X¹, X², X³, X⁴, X⁵ and X⁶ in aboveFormulas (IV) to (IX) include those illustrated and discussed above asrepresenting Z¹ to Z¹¹, except condensated aryl radicals.

Illustrative radicals represented by Y¹, Y², Y³, Y⁴ and Y⁵ in aboveFormulas (IV) to (IX) include those illustrated and discussed above asrepresenting Z¹ to Z¹¹, except condensated aryl radicals.

More preferably, X¹ is the same as X² and Z¹ is the same as Z² inFormula (IV), X³ is the same as X⁴, Z³ is the same as Z⁴, and Y¹, Y² arehydrogen radicals in Formula (V), Z⁶ is a hydrogen radical in Formula(VII), Z⁸ is the same as Z⁹ in Formula (VIII), Z¹⁰ is the same as Z¹¹and Y⁴ and Y⁵ are hydrogen radicals in Formula (IX).

Specific illustrative examples of the bisphosphite ligands employable inthis invention include such preferred ligands as:3,3′-bis(carboxyisopropyl)-1,1′-binaphthyl-2,2′-diyl-bis[bis(1-naphthyl)]phosphitehaving the formula:

[3,3′-bis(t-butyl)-5,5′-dimethoxy-1,1′-biphenyl-2,2′diyl]-bis(oxy)]-bis(dibenzo[d,f][1,3,2])dioxaphosphepin having the formula:

3,3′-bis(carboxyisopropyl)-1,1′-binaphthyl-2-yl-bis[(1-naphthyl)]phosphite-2′-yl-oxy-dibenzo[d,f][1,3,2]dioxaphosphepinhaving the formula:

5,5′-bis(t-butyl)-3,3′-dimethoxy-1,1′-biphenyl-2,2′-diyl-bis[bis(1-naphthyl)]phosphitehaving the formula:

3,3′-bis(carboxymethyl)-1,1′-binaphthyl-2,2′-diyl-bis[bis(2-t-butylphenyl)]phosphitehaving the formula:

[3,3′-bis(t-butyl)-5,5′-dimethoxy-1,1′-biphenyl-2,2′-diyl]-bis(oxy)]-bis([1,1′-dinaphto[d,f][1,3,2])dioxaphosphepin having the formula:

and the like.

Such types of bisphosphite ligands employable in this invention and/ormethods for their preparation are well known as seen disclosed forexample in U.S. Pat. Nos. 4,668,651; 5,288,918; 5,710,306, the entiredisclosure of which is incorporated herein by reference thereto.

In general, such hydroformylation reactions involve the production ofaldehydes by reacting an olefinically unsaturated compound with carbonmonoxide and hydrogen in the presence of a rhodium-organobisphosphitecomplex catalyst in a liquid medium that also contains a solvent for thecatalyst. The process may be carried out in a continuous single passmode or more preferably in a continuous liquid catalyst recycle manner.The recycle procedure generally involves withdrawing a portion of theliquid reaction mixture containing the catalyst and aldehyde productfrom the hydroformylation reaction zone, either continuously orintermittently, and distilling aldehyde product therefrom in one or morestages, in a separate distillation zone in order to recover aldehydeproduct and other volatile materials in vaporous form, thenon-volatilized rhodium catalyst containing residue being recycled tothe reaction zone. Likewise, the recovered non-volatilized rhodiumcatalyst containing residue can be recycled with or without furthertreatment to the hydroformylation zone in any conventional mannerdesired. Accordingly, the processing techniques of this invention maycorrespond to any known processing techniques such as heretoforeemployed in conventional liquid catalyst recycle hydroformylationreactions.

As noted above the hydroformylation reaction conditions that may beemployed in the hydroformylation processes encompassed by this inventionmay include any suitable continuous hydroformylation conditionsheretofore disclosed in the above-mentioned patents. Further, thehydroformylation process may be conducted at a reaction temperature fromabout 25° C. to about 150° C. In general hydroformylation reactiontemperature of about 70° C. to about 120° C. are preferred for all typesof olefinic starting materials, the more preferred reaction temperaturesbeing from about 90° C. to about 100° C. and most preferably about 95°C.

The olefinic starting material reactants that may be employed in thehydroformylation reactions encompassed by this invention includeolefinic compounds containing from 2 to 30 carbon atoms. Such olefiniccompounds can be terminally or internally unsaturated and be ofstraight-chain, branched chain or cyclic structures, as well as beolefin mixtures, such as obtained from the oligomerization of propene,butene, isobutene, etc., (such as so called dimeric, trimeric ortetrameric propylene, and the like, as disclosed, e.g., in U.S. Pat.Nos. 4,518,809 and 4,528,403). Moreover, mixtures of two or moredifferent olefinic compounds may be employed as the startinghydroformylation material if desired. Further such olefinic compoundsand the corresponding aldehyde products derived therefrom may alsocontain one or more groups or substituents which do not unduly adverselyaffect the hydroformylation process or the process of this inventionsuch as described, e.g., in U.S. Pat. Nos. 3,527,809; 4,668,651 and thelike.

Illustrative olefinic unsaturated compounds are alpha-olefins, internalolefins, alkyl alkenoates such as methyl-2-pentenoate,methyl-3-pentenoate and methyl-4-pentenoate, alkenyl alkanoates, alkenylalkyl ethers, alkenols, and the like, e.g., ethene, propene, 1-butene,1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene,1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene,1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene, 2-butene,2-methyl propene (isobutylene), 2-methylbutene, 2-pentene, 2-hexene,3-hexene, 2-heptene, cyclohexene, 2-ethyl-1-hexene, 2-octene, allylalcohol, allyl butyrate, hex-1-en-4-ol, oct-1-en-4-ol, vinyl acetate,allyl acetate, 3-butenyl acetate, vinyl propionate, allyl propionate,methyl methacrylate, vinyl ethyl ether, vinyl methyl ether, allyl ethylether, n-propyl-7-octenoate, 3-butenenitrile, 3-pentenenitrile and5-hexenamide.

Of course, it is understood that mixtures of different olefinic startingmaterials can be employed, if desired, by the hydroformylation processof the subject invention. More preferably the subject invention isespecially useful for the production of aldehydes, by hydroformylatingalpha olefins containing from 2 to 20 carbon atoms, includingisobutylene, and internal olefins containing from 4 to 20 carbon atomsas well as starting material mixtures of such alpha olefins and internalolefins. Still more preferably the subject invention is especiallyuseful for the production of aldehydes from methyl-3-pentenonate, in anyisomeric form, or mixture of isomeric forms.

As noted above the hydroformylation reaction conditions that may beemployed in the hydroformylation processes encompassed by this inventionmay include any suitable continuous hydroformylation conditionsheretofore disclosed in the above-mentioned patents. For instance, thetotal gas pressure of hydrogen, carbon monoxide and olefinic unsaturatedstarting compound of the hydroformylation process may range from about 1to about 10,000 psia. In general, however, it is preferred that theprocess be operated at a total gas pressure of hydrogen, carbon monoxideand olefinic unsaturated starting compound of less than about 1500 psiaand more preferably less than about 500 psia. The minimum total pressurebeing limited predominately by the amount of reactants necessary toobtain a desired rate of reaction. More specifically the carbon monoxidepartial pressure of the hydroformylation process of this invention ispreferable from about 1 to about 120 psia, and more preferably fromabout 3 to about 90 psia, while the hydrogen partial pressure ispreferably about 15 to about 160 psia and more preferably from about 30to about 100 psia. In general H₂:CO molar ratio of gaseous hydrogen tocarbon monoxide may range from about 1:10 to 100:1 or higher, the morepreferred hydrogen to carbon monoxide molar ratio being from about 1:10to about 10:1. The term syn-gas as used herein is understood to mean anygaseous mixture comprised of hydrogen and carbon monoxide.

As noted above, the continuous hydroformylation process of thisinvention involves the use of a rhodium-organobisphosphite ligandcomplex catalyst as described herein. Of course mixtures of suchcatalysts can also be employed if desired. The amount ofrhodium-phosphite complex catalyst present in the reaction mixture of agiven hydroformylation process encompassed by this invention need onlybe that minimum amount necessary to provide the given rhodiumconcentration desired to be employed and which will furnish the basisfor at least the catalytic amount of rhodium necessary to catalyze theparticular hydroformylation process involved such as disclosed e.g. inthe above-mentioned patents. In general, rhodium concentrations in therange of from about 10 ppm to about 1000 ppm, calculated as freerhodium, in the reaction mixture should be sufficient for mostprocesses, while it is generally preferred to employ from about 10 to500 ppm of rhodium and more preferably from 25 to 350 ppm to rhodium.

In addition to the rhodium-organobisphosphite catalyst thehydroformylation process encompassed by this invention may be carriedout in the presence of free organobisphosphite ligand, i.e. ligand thatis not complexed with the rhodium metal of the complex catalystemployed. Said free organobisphosphite ligand may correspond to any ofthe above defined organobisphosphite ligands discussed above asemployable herein. When employed it is preferred that the freeorganobisphosphite ligand be the same as the organobisphosphite ligandof the rhodium-organobisphosphite complex catalyst employed. However,such ligands need not be the same in any given process. Moreover, whileit may not be absolutely necessary for the hydroformylation process tobe carried out in the presence of any such free organobisphosphiteligand, the presence of at least some amount of free organobisphosphiteligand in the reaction mixture is preferred. Thus the hydroformylationprocess of this invention may be carried out in the absence or presenceof any amount of free organobisphosphite ligand, e.g. up to 100 moles,or higher per mole of rhodium metal in the reaction mixture. Preferablythe hydroformylation process of this invention is carried out in thepresence of from about 1 to about 50 moles of organobisphosphite ligand,and more preferably from about 1 to about 4 moles of organobisphosphiteligand, per mole of rhodium metal present in the reaction mixture; saidamounts of organobisphosphite ligand being the sum of both the amount oforganobisphosphite ligand that is bound (complexed) to the rhodium metalpresent and the amount of free (non-complexed) organobisphosphite ligandpresent. Of course, if desired, make-up or additional organobisphosphiteligand can be supplied to the reaction mixture of the hydroformylationprocess at any time and in any suitable manner, e.g. to maintain apredetermined level of free ligand in the reaction mixture.

The hydroformylation reactions encompassed by this invention may also beconducted in the presence of an organic solvent for therhodium-organobisphosphite complex catalyst and any freeorganobisphosphite ligand that might be present. Any suitable solventwhich does not unduly adversely interfere with the intendedhydroformylation process can be employed. Illustrative suitable solventsfor rhodium catalyzed hydroformylation processes include those disclosede.g. in U.S. Pat. No. 4,668,651. Of course mixtures of one or moredifferent solvents may be employed if desired. Most preferably thesolvent will be one in which the olefinic starting material, andcatalyst, are all substantially soluble. In general, it is preferred toemploy aldehyde compounds corresponding to the aldehyde products desiredto be produced and/or higher boiling aldehyde liquid condensationby-products as the primary solvent, such as the higher boiling aldehydeliquid condensation by-products that are produced in situ during thehydroformylation process. Indeed, while one may employ any suitablesolvent at the start up of a continuous process, the primary solventwill normally eventually comprise both aldehyde products and higherboiling aldehyde liquid condensation by-products due to the nature ofsuch continuous processes. Such aldehyde condensation by-products canalso be preformed if desired and used accordingly. Of course, the amountof solvent employed is not critical to the subject invention and needonly be that amount sufficient to provide the reaction mixture with theparticular rhodium concentration desired for a given process. Ingeneral, the amount of solvent may range from 0 percent by weight up toabout 95 percent by weight or more based on the total weight of thereaction mixture.

The distillation and separation of the desired aldehyde product from therhodium-bisphosphite complex catalyst containing product solution maytake place at any suitable temperature desired. In general it isrecommended that such distillation take place at low temperatures, suchas below 150° C., and more preferably at a temperature in the range offrom about 50° C. to about 130° C., and most preferably between 70 and115° C. It is also generally recommended that such aldehyde distillationtakes place under reduced pressure, e.g. a total gas pressure that issubstantially lower than the total gas pressure employed duringhydroformylation when low boiling aldehydes (e.g. C₄ to C₆) are involvedor under vacuum when high boiling aldehydes (e.g. C₇ or greater) areinvolved. In general distillation pressures ranging from vacuumpressures or below on up to total gas pressure of about 50 psig shouldbe sufficient for most purposes.

Of course it is to be understood that while the optimization of thesubject invention necessary to achieve the best results and efficiencydesired are dependent upon one's experience in the utilization of thesubject invention, only a certain measure of experimentation should benecessary to ascertain those conditions which are optimum for a givensituation and such should be well within the knowledge of one skilled inthe art and easily obtainable by following the more preferred aspects ofthis invention as explained herein and/or by simple routineexperimentation.

Finally, the aldehyde products of the hydroformylation process of thisinvention have a wide range of utility that is well known and documentedin the prior art e.g. they are especially useful as starting materialsfor the production of alcohols and acids, as well as for the productionof monomeric and polymeric compounds such as ε-caprolactam, adipic acid,nylon-6 and nylon-6,6.

The following examples are illustrative of the present invention and arenot be regarded as limitive. It is to be understood that all of theparts, percentages and proportions referred to herein and in theappended claims are by weight unless otherwise indicated.

EXAMPLE 1

In a continous process, methyl-3-pentenoate was hydroformylated using arhodium/naftol-3 (ligand with structure XII) catalyst. The reactiontemperature was 95° C. and the pressure was 0.5 MPa. The molar ratio ofhydrogen to carbon monoxide was 1:1. A rhodium concentration of 150 ppmwwas applied with a small molar excess of ligand (ligand/Rh=1.1). Theligand concentration was kept at a constant level by continuous feed ofmake-up ligand to the reactor. The average hold-up time in the stirredcontinuous tank reactor was approximately 4 hours. The liquid reactoreffluent was flashed to atmospheric pressure to removed a large part ofthe dissolved gasses. After this flash, the liquid was passed to avacuum evaporator where most of the unconverted substrates and thealdehyde products were removed as overheads. The overhead products werecollected and analyzed by Gas chromatographic techniques. The bottomstream, containing the non volatile catalyst was continuously recycledto the reactor. During the run the conversion was determined to be 84%to methyl-5-formylvalerate. The STY (space time yield) was estimated at0.65 mole M5FV/ltr.hr.

Comparative Experiment A

Performed as described in Example 1 using a methyl-3-pentenoate feedthat was contaminated with trace amounts of 1,3-butadiene (250 ppm). Thecatalyst activity reduced to 0.05 mole M5FV/ltr.hr and hence thecatalyst showed negligible activity.

EXAMPLE 2

Comparative Experiment A was continued by reducing the methyl-pentenoatefeed to a stop, and to raise the pressure of the reactor to 7 MPa for 2cycles, i.e. the time required for the whole catalyst inventory to spendthe 4 hour hold-up time in the reactor, to pass the separation, section,and to recycle back to the reactor. Then the pressure was reduced to 0.5MPa and the feed was re-started using the non-contaminatedmethyl-3-pentenoate, initially at such a rate sufficient to restore theinitial catalyst concentration. The catalyst activity was recovered tothe normal value of STY of 0.6 mole M5FV/ltr.hr.

1. A continuous hydroformylation process for producing an aldehyde comprising 1) reacting an olefinically unsaturated compound, carbon monoxide and hydrogen in the presence of a rhodium-organobisphosphite complex catalyst at a partial pressure of carbon monoxide and hydrogen, and 2) exposing a mixture comprising at least a portion of the catalyst of 1) to a gaseous mixture comprising hydrogen at a pressure that is greater than the partial pressure of carbon monoxide and hydrogen during the reaction.
 2. Process according to claim 1, wherein the gaseous mixture comprises hydrogen and carbon monoxide.
 3. Process according to claim 1, wherein aldehyde product is separated from the catalyst by distilling the hydroformylation reaction mixture and wherein at least a part of the hydroformylation reaction mixture is exposed to the gaseous mixture prior to distillation.
 4. The process according to claim 1, wherein the pressure used in step 2) is between 3 and 20 MPa.
 5. The process according to claim 4, wherein the pressure used in step 2) is between 3 and 10 MPa.
 6. The process according to claim 1, wherein step 2) is performed in a vessel which is separate from the reaction vessel.
 7. A hydroformylation process comprising: a) reacting an olefinically unsaturated compound, with carbon monoxide and hydrogen at a partial pressure of hydrogen and carbon monoxide in the presence of a rhodium-organobisphosphite complex catalyst to produce a hydroformylation reaction mixture, b) separating aldehyde product from catalyst by heating the hydroformylation reaction mixture, resulting in an aldehyde product containing stream and a recyclable catalyst containing stream, wherein at least a portion of the hydroformylation reaction mixture and/or a portion of the recyclable catalyst containing stream is treated with a gaseous mixture comprising hydrogen at a partial pressure greater than the partial pressures in a).
 8. The process according to claim 1, wherein the organobisphosphite ligand of said rhodium-organobisphosphite complex catalyst is a ligand selected from the class consisting of

wherein each R¹ represents a divalent radical selected from a group consisting of alkylene, alkylene-(Q)_(n)-alkylene, arylene and arylene-(Q)_(n)-arylene, and wherein each alkylene radical individually contains from 2 to 18 carbon atoms and is the same or different, and wherein each arylene radical individually contains from 6 to 18 carbon atoms and is the same or different; wherein each Q individually represents a divalent bridging group of —O— or —CR′R″— wherein each R′ and R″ radical individually represents hydrogen or a methyl radical; and wherein each n individually has a value of 0 or 1, wherein R², R³, R⁴, and R⁵ might be the same or different and each is individually represented by the structure of (VI) or (VII),

wherein R⁶ and R⁷ might be the same or different and each is individually represented by the structure of (VIII) or (IX),

wherein, X⁵ and X⁶ might be the same or different and each individually represents a hydrogen or an organic radical, wherein Y³, Y⁴ and Y⁵ are the same or different and each represents a hydrogen or alkyl radical, wherein Z⁵, Z⁶, Z⁷, Z⁸, Z⁹, Z¹⁰ and Z¹¹ might be the same or different and each represent a hydrogen or an organic radical placed at any remaining position of the aryl rings.
 9. The process of claim 8, wherein R¹ is represented by the structure of (IV), (V),

(VIII) or (IX), wherein X¹, X², X³, X⁴, X⁵ and X⁶ might be the same or different and each individually represents a hydrogen or an organic radical, wherein Y¹, Y², Y⁴ and Y⁵ are the same or different and each represents a hydrogen or an alkyl radical, wherein Z¹, Z², Z³, Z⁴, Z⁸, Z⁹, Z¹⁰ and Z¹¹ might be the same or different and each represent a hydrogen or an organic radical placed at any remaining position of the aryl rings of structures, wherein X¹ is the same as X² and Z¹ is the same as Z² in Formula (IV), X³ is the same as X⁴, Z³ is the same as Z⁴, and Y¹ and Y² are hydrogen radicals in Formula (V), Z⁸ is the same as Z⁹ in Formula (VIII), Z¹⁰ is the same as Z¹¹ and Y⁴ and Y⁵ are hydrogen radicals in Formula (IX).
 10. The process according to claim 8, wherein the ligand used is [3,3′-bis(t-butyl)-5,5′-dimethoxy-1,1′-biphenyl-2,2′-diyl]-bis(oxy)]-bis(dibenzo[d,f][1,3,2])dioxaphosphepin, 3,3′-bis(carboxyisopropyl)-1,1′-binaphthyl-2,2-diyl-bis[bis(1-naphthyl)]phosphite and 3,3′-bis(carboxymethyl)-1,1′-binaphthyl-2,2′-diyl-bis[bis(2,5-di-t-butyl)]phosphite. 